Self-sprung stabilization fin system for gun-launched artillery projectiles

ABSTRACT

A system and process for the aerodynamic stabilization of rocket-assisted artillery projectiles launched from smooth-bore cannons comprises multiple stabilization fins stowed circumferentially and held by a cap until muzzle exit. At muzzle exit, the cap separates and allows the fins to self-deploy using the energy stored within the fin material, which is either shape memory alloy or spring steel. The fins are then locked into place and serve to stabilize the projectile without interfering with the discharge of hot propelling gasses from the rocket nozzle.

GOVERNMENT INTEREST

The embodiments described herein may be manufactured, used, and licensed by or for the United States Government without the payment of royalties thereon.

BACKGROUND

1. Technical Field

The embodiments herein generally relates to artillery projectiles, and, more particularly to fin deployment systems used on artillery projectiles.

2. Description of the Related Art

Coil-spring deployed stabilization fins typically found on missiles generally cannot be adapted to gun-launched artillery projectiles because they would be subjected to the harsh hyper acceleration environment of guns. As used herein, the term “gun” and “guns” is meant to include cannons, mortars, howitzers and other tubular structures that can be used to launch projectiles. Structural members would be placed under significant compressive and tensile loads. Often, these loads are not well understood, difficult to model and cause the hinges, springs, and their points of attachment to fail. The projectile then becomes unstable in flight with potentially catastrophic results. Furthermore, the curved “wrap-around” style typically cannot be used on rocket-assisted gun-launched projectiles due to the projectile's change to subsonic velocity near the end of the trajectory where such fins would create a “roll reversal” and destabilize the projectile just before impact. Therefore, only flat fins are acceptable for stability over the entire velocity spectrum.

Other types of deployable fins meeting the flat criteria on cannon-launched artillery are of the “jack-knife blade” design and are folded forward for launch. When the projectile exits the cannon, these fins fold out and back and lock into position to stabilize the projectile. These motor-driven fins have been successful on non-rocket assisted projectiles or with rocket-assisted projectiles utilizing a small diameter nozzle for long flight. For rocket-assisted projectiles with a large-diameter rocket nozzle, the knife blade type of system tends to intrude into the rocket nozzle when stowed and block the rocket gas flow when deployed. While the conventional designs provided adequate solutions for the purposes for which they were designed, there remains a need for a new fin deployment system for use in large diameter rocket nozzles used to deploy artillery projectiles.

SUMMARY

In view of the foregoing, an embodiment herein provides a system for the flight stabilization of gun-launched rocket-assisted artillery projectiles that accommodate a large-diameter rocket nozzle and operate in sonic and subsonic flight regimes. The system is attached as a base on the aft of the projectile that houses a rocket subsystem and is stowed in a cylindrical enclosure by a lightweight, self-disintegrating protective cap. In certain desirable embodiments, the fins of the projectiles are fabricated of a shape memory alloy or a spring steel and deploy at muzzle exit and lock at 90° to a plane tangent to the cylindrical surface of the base. The system is used in conjunction with specialized rocket-assisted artillery projectiles having an unusually large exit diameter on the nozzle. The present invention also provides a toy or another amusement device, for example pyrotechnics, with any of the features and advantages described herein.

These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:

FIG. 1 is a perspective view of a fin system in a flight configuration according to an embodiment herein;

FIG. 2 is a perspective view of a fin attachment plate according to an embodiment herein;

FIG. 3(A) is a perspective view of a fin system with the fins compressed against the hub according to an embodiment herein;

FIG. 3(B) is a perspective view of a fin in a conformed shape according to an embodiment herein;

FIG. 4 is a perspective view of a spacer according to an embodiment herein;

FIG. 5 is a perspective view of a fin deployment assembly with spacers in place over the conformed fins and an end cap according to an embodiment herein;

FIG. 6 is a perspective view of a protective cap according to an embodiment herein;

FIG. 7 is a perspective view of a fin deployment assembly with a protective cap according to an embodiment herein; and

FIG. 8 is a flow diagram illustrating a preferred method according to an embodiment herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

As mentioned, there remains a need for a new fin deployment system for use in large-caliber artillery projectiles employing large-diameter rocket nozzles. The embodiments herein achieve this by providing a self-sprung stabilization fin system for gun-launched rocket-assisted artillery projectiles. Referring now to the drawings, and more particularly to FIGS. 1 through 8, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

Referring now to FIG. 1, an inventive process is applied to an artillery projectile 100 to provide in-flight aerodynamic stability. A projectile stabilization system 110 of deployable fins 120 is affixed to the aft end 180 of the projectile 100, shown in FIG. 1 in a flight configuration after the projectile 100 has cleared the cannon (not shown). Each of the fins 120, which are each preferably rectangular in shape, is affixed to a hub 130 by means of a hinge pin 140. While the drawings depict four fins 120, the embodiments herein are not restricted to exactly four fins 120. Preferably, three or more fins 120 are affixed to the hub 130. The pin 140 is held in place at each end by a hole (not shown) drilled into a boss 150 at the fore end 160 and into holes 165 (shown in FIG. 2) in a corresponding aft plate 170 at the aft end 180 of the projectile 100 (of FIG. 1). Once deployed, the tins 120 are constrained from further tangential rotation by a key notch 190 into which the fins 120 are set backwards by residual muzzle exit acceleration.

Referring to FIG. 3(A), the fins 120 are forced down onto the hub 130 temporarily by a system of hose clamps (not shown) which are gradually tightened and protected by nylon (or similar soft material) spacers 200, which are further shown in FIG. 4. A fin 120 in the stowed (compressed) state is shown in FIG. 3(B). The fins 120 wrap around the hub 130 when stowed and then deploy flat at muzzle exit. A longitudinal hinge pin 140 is connected along the edge of the fin 120 and is affixed to the hub 130. Referring to FIG. 5, after the spacers 200 and fins 120 are clamped all the way down onto the hub 130 thus conforming to the hub 130, a closure cap 210, which may comprise steel, may be placed over the opening, convex side out, covering the rocket nozzle exit orifice. The closure cap 210 prevents high pressure burning gun gasses from entering the inside of the projectile 100. The cap 210 holds the fins 120 to a curved shape and conforms the fins 120 to the cylindrical hub 130. The cap 210, which may be embodied as the cap described in U.S. Pat. No. 6,435,097, the complete disclosure of which, in its entirety, is herein incorporated by reference, is adapted to disintegrate at muzzle exit releasing the fins 120. The energy that is stored within the material of the fins 120 to conform them to the cylindrical hub 130 is then released and as the fins 120 return to their original flat state, they are thrust into flight position and are locked into at least one key notch 190.

Referring to FIG. 6, a protective sacrificial cap 500, preferably comprising fiberglass, is shown. The cap 500 is pressed over the system 110 and as it stops against each temporary clamp (not shown), the clamp is removed and the pressing is continued until all clamps are removed and the cap 500 is tight against the boss 150 as shown in FIG. 7. At this point, any voids under the cap 500 where the fins 120 are folded are preferably filled with an incompressible gel (not shown) to prevent hot gun gasses from penetrating the protective sacrificial cap 500 at such locations. One suggested incompressible gel includes, but is not limited to, sodium carboxymethyl cellulose. Other viscous aqueous gels or other viscous gels, including non-aqueous may be used. As used herein, the term “gel” may also include liquids but is preferably a semisolid material or a semirigid colloidal dispersion. As used herein, the term “incompressible” with respect to gels is meant to include gels that do not compress appreciably under large increases in pressure. Preferably, the gel does not decrease in volume by more than about 3 percent under pressures encountered during launch. More preferably, the gel does not decrease in volume by more than about 2 percent under pressures encountered during launch. Still more preferably, the gel does not decrease in volume by more than about 1 percent under the pressures encountered during launch. The gel acts as a hydrostatic incompressible resistance to the pressure. This step is accomplished by piercing the fiberglass protective sacrificial cap 500 with an industrial syringe filled with an aqueous gel. The gel is transferred inside the cap 500 until all voids are filled. The point of penetration is sealed with a silicone compound. When the projectile 100 is fired, the gel along with the cap 500 is substantially destroyed.

The embodiments herein provide a system 110 and a process for aerodynamically stabilizing rocket-assisted artillery projectiles 100 launched from smooth-bore cannons. The fins 120 are preferably fabricated from a shape memory alloy or a spring steel. The energy stored within the fins 120 by compressing them down to conform to the cylindrical hub 130 is sufficient to deploy the fins 120 at muzzle exit into a position perpendicular to the circumference of the hub 130. Then, residual acceleration at muzzle exit sets the fins 120 back into a notch 190, locking them in place.

FIG. 8, with reference to FIGS. 1 through 7, illustrates a method of providing in-flight aerodynamic stability of rocket assisted artillery projectiles 100 launched from a smooth-bore cannon (not shown) according to an embodiment herein, wherein the method comprises storing (301) a projectile system 110 in the cannon, wherein the projectile system 110 comprises a projectile 100; a generally cylindrical hub 130 operatively connected to the projectile 100; an end plate 170 attached to the hub 130; multiple fins 120 hinged along a circumferential periphery of the hub 130; a sacrificial cap 500 encapsulating the multiple fins 120 and the hub 130. The method further comprises injecting (303) a sacrificial incompressible aqueous gel (not shown) into voids between stowed fins 120 within the cap 500; launching (305) the projectile system 110 from a muzzle (not shown) of the cannon; and the sacrificial cap 500 separating (307) from the multiple fins 120 and the hub 130. Preferably, residual muzzle exit acceleration forces the multiple fins 120 into notches 190 in the end plate 170 thereby locking the multiple fins 120 into a deployed flight position that make the multiple fins 120 perpendicular to the hub 130. Moreover, at muzzle exit, the sacrificial cap 500 is preferably adapted to separate from the multiple fins 120, the hub 130, and the end plate 170 thereby allowing the multiple fins 120 to self-deploy using potential energy stored within the multiple fins 120. Preferably, the multiple fins 120 are adapted to conformably fit around an outer surface of the hub 130 when the multiple fins 120 are in a stowed configuration. Furthermore, the fins 120 preferably comprise a shape memory alloy material or a spring steel material. The system 110 may further comprise an adapter (not shown); a generally cylindrical boss 150 operatively connected to the adapter, wherein the adapter connects the projectile 100 to the hub 130; hinge pins 140 connected to the boss 150, wherein the hinge pins 140 operatively connect the fins 120 to the hub 130; and a closure cap 210 operatively connected to the hub 130 and adapted to hold the fins 120 to a curved shape and conform the fins 120 to the hub 130 when in a stowed configuration. Additionally, the system 110 may further comprise a rocket assist sub module (not shown) housed within the hub 130.

The embodiments herein provide a system 110 and a process that utilizes stored energy within the material of stabilization fins 120 for artillery projectiles 100 launched from smooth-bore cannons making the fins 120 self-deploying and not relying on a separate coil spring, squibs, motor, or other energetic for deployment. The system 110 increases mechanical reliability by reducing the number of moving parts and eliminating the need for electronic signals to ignite energetic materials, typically used in the conventional solutions. The system 110 is unique in that it allows for the large exit-diameter rocket nozzle to function without interference of the exiting propelling gasses. Also, the fins 120 deploy flat, assuring stability at sonic and subsonic velocities. Moreover, the fins 120 do not stow nor interfere with the operation of a rocket assist module (not shown) housed within the hollow fin hub 130.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. For example, many of the features and embodiments of the present invention can be applied to toy rockets and similar amusement devices. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims. 

1. A system for providing in-flight aerodynamic stability to a projectile launched from a gun, said system comprising: a projectile adapted to be launched from a muzzle of a gun; a generally cylindrical hub operatively connected to said projectile; a notched end plate attached to an aft end of said hub; a plurality of equally spaced fins hinged along a circumferential periphery of said hub; a cap encapsulating said fins and said hub; and wherein at muzzle exit, said cap is adapted to separate from said fins, said hub, and said end plate thereby allowing said fins to self-deploy using potential energy stored within said fins.
 2. The system of claim 1, further comprising an incompressible gel buffered within said cap.
 3. The system of claim 1, wherein said fins comprise a spring steel material.
 4. The system of claim 1, wherein residual muzzle exit acceleration forces said fins into a plurality of notches provided in said notched end plate thereby locking said fins into a deployed flight position is substantially perpendicular to said hub.
 5. The system of claim 1, wherein said fins are adapted to conformably fit around an outer surface of said hub when said fins are in a stowed configuration.
 6. The system of claim 1, wherein said gun is a smooth bore cannon.
 7. The system of claim 1, further comprising: an adapter; a generally cylindrical boss operatively connected to said adapter, wherein said adapter connects said projectile to said hub; hinge pins connected to said boss, wherein said hinge pins operatively connect said fins to said hub; and a closure cap operatively connected to said hub and adapted to hold said fins to a curved shape and conform said fins to said hub when in a stowed configuration.
 8. The system of claim 1, further comprising a rocket assist sub module housed within said hub.
 9. A system for providing in-flight aerodynamic stability of projectiles launched from a gun, said system comprising: a projectile adapted to be launched from a muzzle of a gun; a generally cylindrical open-ended hub operatively connected to said projectile; multiple fins hinged along a circumferential periphery of said hub; a sacrificial cap encapsulating said multiple fins and said hub until said projectile exits said muzzle.
 10. The system of claim 9, further comprising an end plate attached to said hub, wherein residual muzzle exit acceleration forces said multiple fins into notches in said end plate thereby locking said multiple fins into a deployed flight position that make said multiple fins perpendicular to said hub.
 11. The system of claim 9, further comprising a gel adapted to fill voids within said cap.
 12. The system of claim 9, wherein said multiple fins comprise a spring steel material.
 13. The system of claim 9, wherein at muzzle exit, said sacrificial cap is adapted to separate from said multiple fins, said hub, and said end plate thereby allowing said multiple fins to self-deploy using potential energy stored within said multiple fins.
 14. The system of claim 9, wherein said multiple fins are adapted to conformably fit around an outer surface of said hub when said multiple fins are in a stowed configuration.
 15. The system of claim 9, further comprising: an adapter; a generally cylindrical boss operatively connected to said adapter, wherein said adapter connects said projectile to said hub; hinge pins connected to said boss, wherein said hinge pins operatively connect said multiple fins to said hub and a closure cap operatively connected to said hub and adapted to hold said fins to a curved shape and conform said fins to said hub when in a stowed configuration.
 16. The system of claim 9, further comprising a rocket assist sub module housed within said hub.
 17. A method of providing in-flight aerodynamic stability to artillery projectiles launched from a gun, said method comprising: storing a projectile system in a gun, wherein said projectile system comprises: a projectile; a generally cylindrical hub operatively connected to said projectile; an end plate attached to said hub; a plurality of fins hinged along a circumferential periphery of said hub; a cap encapsulating said multiple fins and said hub; injecting a gel into voids within said cap; launching said projectile system from a muzzle of said gun; and said cap separating from said multiple fins and said hub.
 18. The method of claim 17, wherein residual muzzle exit acceleration forces said multiple fins into a plurality of notches provided in said end plate thereby locking said multiple fins into a deployed flight position that make said multiple fins perpendicular to said hub.
 19. The method of claim 17, wherein at muzzle exit, said cap is adapted to separate from said multiple fins, said hub, and said end plate thereby allowing said multiple fins to self-deploy using potential energy stored within said multiple fins.
 20. The method of claim 17, wherein said multiple fins are adapted to conformably fit around an outer surface of said hub when said multiple fins are in a stowed configuration. 